Evidence in the literature strongly favors the hypothesis that lactic cultures commonly used in fermentation of milk suppress the formation of colon tumors. However, no controlled experiments have been conducted using animal models to test the hypothesis. Preliminary work in our laboratory (Shackelford et al., Nutr. Cancer, 5:159, 1983) indicates that lactic cultures may suppress the growth of colon carcinoma in animal models. We are proposing to study the effect of feeding supplements of Lactobacillus acidophilus and L. bulgaricus on the incidence of azoxymethane-induced intestinal tumors in rats. Groups of 40 F- 344 male rats will be assigned to 3 dietary treatments at 5 weeks of age. The diets will consist of: (1) semisynthetic diet (SSD) plus L. acidophilus supplement, (2) SSD plus L. bulgaricus supplement and (3) SSD plus uninoculated supplement (control). Supplements will provide approximately 108 viable cells/g diet. The diets will be fed for about 42 weeks. Starting at 7 weeks of age all rats will receive s/c injections of azoxymethane in saline @ 18 mg/kg body weight once a week for 2 weeks. At the end of 47 weeks of age the rats will be sacrificed (or before if moribund) and grossly examined for tumors of various organs, particularly in the small intestines, cecum, colon and rectum. The tumors will be excised, fixed in 10% neutral buffered formalin and subjected to histopathological examination for classification into adenoma and adenocarcinoma. It is hoped that this research, in addition to validating or invalidating the stated hypothesis, will create an environment for future expansion of health-related research resulting in motivation of students to choose health-related careers. An added dimension to the benefits from this research is encouraging minority students (who constitute about 90% of the enrollment at Alabama A&M University) to choose a health-related graduate education.